Figure 4.

Points of interest in the processing steps of TipTracker. Vertical line AB represents the entry of the root at the edge of the image, and the thick black boundary is the root silhouette. Point X represents the initial estimated medial point; dashed lines represent candidate cross-sectional lines through the estimated medial point, the shortest of which is selected as the optimal perpendicular cross section (line Y). A corrected medial point is selected as the midpoint along this optimal cross-sectional line, and its position used to estimate the next medial point in the sequence (point Z).